Electrographic developer

ABSTRACT

A pretoned web mounted upon a supply roll and a takeup roll to form a cassette permits controlled deposition of toner onto a fibrous member by means of mechanical, electrical and triboelectrical forces.

United States Patent [72] Inventor Nicholas M. Soures Penfield, NY. [21 Appl. No. 805,696 [22] Filed Mar. 10, 1969 [45] Patented Oct. 19, 1971 [73] Assignee Xerox Corporation Rochester, N.Y.

[54] ELECTROGRAPHIC DEVELOPER 7 Claims, 4 Drawing Figs.

[52] U.S. Cl 118/637 1 B051 5/00 [50] 1 18/637; 117/175; 346/74 ES, 74 MP [56] References Cited UNITED STATES PATENTS 2,624,652 1/1953 Carlson 117/175 X 2,859,128 11/1958 Matthews et a1 ll7/17.5 2,901,374 8/1959 Gundlach 117/17.5 2,902,974 9/1959 Greaves..... l17/l7.5 X 2,959,153 11/1960 118/637 2,974,632 3/1961 118/637 3,147,679 9/1964 Schaffert 117/175 UX 3,216,844 11/1965 117/17.5 3,220,831 11/1965 McFarlane 118/637 X Primary Examiner-Morris Kaplan Attorneys-James J. Ralabate, Laurence A, Wright and John E. Beck ABSTRACT: A pretoned web mounted upon a supply roll and a takeup roll to form a cassette permits controlled deposition of toner onto a fibrous member by means of mechanical, electrical and triboelectrical forces.

PATENTEU 19 3.613.636

INVENTOR. NICHOLAS M. SOURES AT TORNE Y ELECTROGRAPHIC DEVELOPER This invention relates to electrography. More particularly, this invention relates to an apparatus for developing the electrostatic latent image on charged surfaces by depositing electroscopic developer particles or toner thereon.

In the conventional xerographic process a uniform electrostatic charge is placed upon a photoconductive surface by a charging device. Subsequently, parts of the surface are discharged by exposure to light. In other electrographic processes an electrostatic pattern or image is formed directly on the insulating surface corresponding to the original pattern or image to be reproduced. In order to form a visible rendering of either electrostatic image it is necessary to develop the image with electroscopic powder or toner. A toner is selected such that it will be charged to a polarity opposite to that of the electrostatic image. When the oppositely charged toner is deposited on the image surface having an electrostatic charge, the charge on the image exerts a force of attraction on the toner and retains the toner in the charged areas. By this means the image is made visible.

In the development process the objective sought is a reproduction of the original which has sharp contrast and which is free of background smudging. The development of the electrostatic latent image can be achieved by employing several techniques. Among these is the technique of cascading electroscopic powder or toner on to the surface carrying the image and transferring this developed image to a recording sheet or web while in contact with the image-carrying surface and thereafter fixing the toner image by application of heat to the recording means. For an example of cascade development see US. Pat. No. 2,990,278 to Carlson. Another technique of developing conforms in many respects to that just described except that a powder cloud of developer particles or toner is dispersed over the surface bearing the latent image. The powder cloud development technique is discussed further in US. Pat. No. 3,239,465. Still another technique of developing is to deposit toner on the charged surface by means of a magnetic brush set forth in US. Pat. No. 2,791,949. The magnetic brush is composed of a mass of very small iron particles which form fibers" under the influence of a magnetic field. When the desired developer or toner is mixed with the magnetic powder it is charged triboelectrically and upon being picked up by a magnet a brush is formed with charged toner particles adhering in a random manner to the iron fibers. Yet another technique of image development is to deposit toner by means of a fur brush impregnated with toner. Fur brush development is further exemplified in US. Pat. No. 3,251,706. This invention is concerned with improvements in a fur brush development system.

All of the above image-developing techniques have performed satisfactorily in practical xerographic printers. However, each of these approaches or methods have advantages and disadvantages which make one more acceptable over the other in a desired machine. For example, the technique of cascade developing may be undesirable because it depends upon gravity flow and causes abrasion on the dielectric surface in addition to being expensive to construct as well as being bulky. Similar objections can be ascribed to the method of powder cloud development. There, the powder cloud is usually created by dispersing the toner particles under air pressure through a nozzle on to the charged surface. Here also, the mechanism necessary to create the powder cloud is generally expensive and bulky. The magneticbrush-developing method furnishes well developed solid area images however, continuous tone images are reproduced with excessive contrast. Here again, bulk and economies are factors to be reconciled.

Fur brush development processes taught by the prior art have the disadvantage that the amount of toner applied to the brush could not be easily controlled. Where unequal amounts of toner is applied to the fibrous member or fur brush the developed images may have light and dark areas as well as undesirable background smudges. The present invention provides an improved, simply designed and comparatively inexpensive fur brush developer employing a pretoned belt. The fibrous member of the invention picks up controlled amounts of toner from a pretoned belt or web which is in the form of a cassette having a supply roll and a takeup roll. The web has a first or top layer uniformly coated with developer particles or toner and a second or bottom layer made of conductive foil. When the fibrous member moves across the coated layer of the pretoned web it picks up a uniform amount of toner and deposits it on to the charged surface which is developed thereby. This method of toning removes the need for toner agitation and mechanical toner regulation. There is also no longer any need for a donor roller or a wiper to control loading of the donor roller. It also has the advantage of allowing the pretoned web to be advanced incrementally as a function of paper advance. When formed into a cassette configuration the pretoned web has a simple loading procedure and is disposable after use. Also the operator replacing the cassette finds it a cleaner system than the handling of loose toner. The pretoned web furnishes uniform toner coating which is independent of time. Also by varying the pretoned web displacement the uniform amount of toner presented to the fibrous member can be varied as a function of time. The result is that the image density can be simply adjusted by the operator.

It is an object of the present invention to provide for deposition of developer or toner on to a surface bearing an electrostatic latent image wherein a fur brush collects toner from a pretoned web and then uniformly applies the toner to an image bearing surface.

It is a further object of the invention to provide a disposable and easily interchangeable pretoned web in the form of a cassette in a developer system.

In order to gain a better understanding of the invention, as well as other objects and further features thereof, reference is made to the following detailed description to be read in conjunction with the accompanying drawings wherein:

FIG. 1 is a side view of a section of the pretoned web;

FIG. 2 is a diagrammatic side view of pretoned web and brush developer system;

FIG. 3 is a side view of the pretoned web cassette mounted for operation; and

FIG. 4 is a view similar to FIG. 3 with the pretoned web cassette removed from its mounting.

The present invention is particularly intended and adapted for the development of an electrostatic latent image such as particularly a latent image of relatively fine detail composed of relative charged and uncharged areas on an insulating surface. The development technique taught by the present invention may be employed to apply toner directly to a photoconductive surface or to electrostatic recording paper bearing an electrostatic latent image.

Illustrated in FIG. 1 there is shown generally at 10 a section of pretoned web. The web may for example comprise a layer of paper 12 and a conductive layer of foil 13 which may be aluminum or other conductive material. Other web material which would perform satisfactorily may be felt, plastic or fiber glass. Coated upon the paper layer I2 are electroscopic developer particles or toner 11. The toner is applied uniformly to the paper layer and is held there by mechanical and triboelectric forces.

An advantage of the pretoned web is that webs can be made having the desired amount of toner coating for different applications. Another advantage inherent in the pretoned web is that the conductive backing permits biasing of the web to control toner deposition to a fur brush. That is, an operator may adjust the bias on the conductive layer to control toner deposition and thus copy background within controlled limits. The web donor system may be considered analagous to the ribbon in a typewriter in that each time there is a line advance on the copy the web is advanced. When the web is placed in a car tridge or cassette a new web is easily changed by the operator and the old web discarded.

Referring now to FIG. 2 there is illustrated diagrammatb cally a developer system employing the novel pretoned web of the invention. Reference 10 is the pretoned web having a flat paper layer with an aluminum backing. The web is mounted on supply roll 14 which rotates on shaft 16 and is mounted on suitable support means to be disclosed hereinafter. A takeup roll 17 mounted on shaft 18 for rotation and similarly supported receives the used up portion of the web after the toner has been removed by cylindrical fibrous member or brush 21.

Bias bar 19 is in contact with the conductive layer of pretoned web 10 and may have a bias potential thereon or be grounded. When a negative bias potential is placed on bias bar 19 by adjustable voltage V, toner will be repelled from the pretoned web on to the fibrous member 21. Alternately, a positive voltage may be placed on bias bar 19 to hold toner on the pretoned web. Thus, an operator may control the amount of toner picked up by the fibrous member by varying the potential on bias bar 19. A stylus carriage member 23 carries stylus arm 22. The stylus arm moves across the charge retaining web or electrostatic paper 26 and as the pins 30 in the stylus are selectively pulsed to the grounded backing electrode 31 a latent electrostatic image is formed on the electrostatic paper web 26. Fibrous member 21 rotates on a shaft and is suitably mounted in contacting relation to electrostatic paper 26 to deposit toner on to the charged surface of electrostatic paper 26. The developed image on electrostatic paper 26 then moves in the direction of platen 24 containing heat element 25 whereby the toner is fused into the paper. Idler rollers 27, 28, 29 guide paper 26 through the recording, developing and fixing stations.

Illustrated in FIG. 3 there is shown a side view of the pretoned web cassette 9 mounted for operation. Reference numeral 40 is a support member which secures the cassette consisting of supply roll 14 and takeup roll 17. Also located on support member 40 are guide pins 43 and 44 and retaining means 42. A locking member 41 having arcuate slots 46 and 47 is provided to engage shafts l6 and 17 of the supply and takeup rolls respectively in the locked position. Retaining means 42 which passes through slot 45 of locking member 4] permits locking member 41 to move between the engaged and released position while still being held by support 40.

In FIG. 4, locking member 41 is shown in its release position allowing the cassette 9 to be removed and replaced. It is contemplated by the invention that once all of the used pretoned web has been loaded on the takeup roll, the exhausted supply roll will be shifted to the place of the takeup roll and loaded for operation. Fibrous member 21 may comprise natural fibers such as rabbit fur or camel's hair. Altemately, the fibrous member may comprise synthetic fibers such as nylon. Takeup roll 17, brush 21 and paper 26 are coupled through the same drive train in order to synchronize the printing, toner dispensing and developing systems. Takeup roll 17 is connected to a drive train (not shown) through a speed reducer (not shown) so that the pretoned web is only advanced a small increment for each rotation of the fur brush. In this way just the right amount of toner is available to the brush for each rotation. The web 10 passes over a bias bar 19 and furnishes a surface where the fur brush 21 may contact the toned surface of the web and also serves as means of keeping the web taut about the supply and takeup rolls.

For optimum image development the web, the toner, and the fibrous member or fur brush should be made from materials arranged in the triboelectric series. In this manner, any material placed in contact with another which is below it in the triboelectric series will become positively charged and the material below it in the series will become negatively charged. Thus, if a positively charged electrostatic image is to be developed an electroscopic powder is selected which is below the charged surface material in the triboelectric series. The electroscopic particles will then become charged to a negative polarity by contact with the charged surface and will be deposited upon the positively charged image by electrical attraction. The pretoned web 10 comprising toner 11 and the fur brush 21 herein are arranged in the triboelectric series described in order totake advantageofseguential toner at;

traction.

In operation of FIG. 2, the motor which drives takeup roll 17, fibrous member 21 and electrostatic-recording paper 26 is initiated. When paper 26 arrives at the recording station stylus '22 forms a latent image thereon. At the same time at the 'developing station, fibrous member 21 has picked up a con- 'trolled amount of toner from web and deposits it upon the charged surface of paper 26. Fibrous member 21 due to its triboelectric properties as explained above removes toner pariticles from the uncharged areas of the charged surface. At the ifusing station comprising platen 24 and heater element 25. the toner is fused into paper 26 to furnish a permanent visible rendering of the image or pattern thereon. Takeup roll is lmounted to move incrementally with paper 26 and because 1 web 10 has a conductive backing the toner deposition on to paper can be electrically controlled by the operator. Allternately, the operator may control the time the fibrous member contacts the pretoned web for purpose of collecting lmore or less toner.

i From the foregoing description it has been established that a pretoned web in the form of an easily interchangeable and @disposable cassette can furnish a means of controlling the aptplication of toner to a charged surface. i What is claimed is:

1. Apparatus for transferring electroscopic developer parti lcles to a charged surface for the development of a latent image thereon comprising:

first means having a first layer carrying a uniform amount of said electroscopic developer particles throughout its length and having a second layer adapted to carry a bias potential thereon, a source of voltage for applying a bias potential to said second layer, and second means having a fibrous surface in contact with said first layer adapted to collect a uniform amount of said developer particles from said first layer and coacting with a bias potential on said second layer to deposit said developer particles on to said charged surface whereby the latent image thereon is developed. 2. Apparatus for transferring electroscopic developer particles to a charged surface for the development of a latent image thereon comprising:

a supply roll, a takeup roll, a web mounted on said supply and takeup rolls said web comprising a first layer coated with said developer particles and a second layer capable of carrying a bias potential,

a source of voltage for applying a bias potential to said second layer, and

a fibrous member in contact with said coated layer of said web adapted to collect a predetermined amount of said developer particles therefrom and in conjunction with the bias potential on said second layer to deposit said developer particles uniformly on to said charged surface whereby the latent image thereon is developed.

3. The apparatus of claim 2 wherein said fibrous member is a cylinder having fur mounted on its surface.

1 4. The apparatus of claim 3 wherein said supply and takeup :rolls of said web are mounted in a cassette so that the con- :sumed web is discarded and replaced.

! S. The apparatus of claim 4 and further comprising a web of electrostatic recording paper bearing said charged surface.

I f6fThe apparatus of claim 5 and further comprising a drive !train coupled to said takeup roll, said fibrous member and said lelectrostatic paper web whereby said fibrous member picks up ;a controlled amount of said particles in synchronism with the incremental movement of said electrostatic paper web.

7. The apparatus of claim 6 wherein said particles, said preton'ed web andsaid fibrous member are arranged in the triboelectric series whereby said particles are attracted in Efifih fforn said pretoned web to said fibrous member and then to said charged surface and whereby said fibrous member attracts said particles away from the uncharged areas of said .sh s dsu as gggg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 636 Dated January 5, 1972 Inventor(s) Nicholas M. Soures It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 4, line 3, change is" to may be--.

Signed and sealed this 11 th day of April 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. Apparatus for transferring electroscopic developer particles to a charged surface for the development of a latent image thereon comprising: first means having a first layer carrying a uniform amount of said electroscopic developer particles throughout its length and having a second layer adapted to carry a bias potential thereon, a source of voltage for applying a bias potential to said second layer, and second means having a fibrous surface in contact with said first layer adapted to collect a uniform amount of said developer particles from said first layer and coacting with a bias potential on said second layer to deposit said developer particles on to said charged surface whereby the latent image thereon is developed.
 2. Apparatus for transferring electroscopic developer particles to a charged surface for the development of a latent image thereon comprising: a supply roll, a takeup roll, a web mounted on said supply and takeup rolls said web comprising a first layer coated with said developer particles and a second layer capable of carrying a bias potential, a source of voltage for applying a bias potential to said second layer, and a fibrous member in contact with said coated layer of said web adapted to collect a predetermined amount of said developer particles therefrom and in conjunction with the bias potential on said second layer to deposit said developer particles uniformly on to said charged surface whereby the latent image thereon is developed.
 3. The apparatus of claim 2 wherein said fibrous member is a cylinder having fur mounted on its surface.
 4. The apparatus of claim 3 wherein said supply and takeup rolls of said web are mounted in a cassette so that the consumed web is discarded and replaced.
 5. The apparatus of claim 4 and further comprising a web of electrostatic recording paper bearing said charged surface.
 6. The apparatus of claim 5 and further comprising a drive train coupled to said takeup roll, said fibrous member and said electrostatic paper web whereby said fibrous member picks up a controlled amount of said particles in synchronism with the incremental movement of said electrostatic paper web.
 7. The apparatus of claim 6 wherein said particles, said pretoned web and said fibrous member are arranged in the triboelectric series whereby said particles are attracted in sequence from said pretoned web to said fibrous member and then to said charged surface and whereby said fibrous member attracts said particles away from the uncharged areas of said charged surface. 